Plastic egg cartons



March 7, 1967 D. c. TRIMBLE 3,

PLASTIC EGG GAR'IONS Filed April 8, 1966 2 Sheets-Sheet 1 DAVID C. TRIMBLE March 7, 1967 D. c. TRIMBLE PLASTIC-EGG CARTONS 2 Sheets-Sheet 2 Filed April 8, 1966 E L B m R T C m m D 8 FIG.5

United States Patent 3,307,765 PLASTIC EGG CARTONS David C. Trimble, Yorklyn, Del., assignor, by mesne assignrnents, to Hercules Incorporated, New Castle County, Del., a corporation of Delaware Filed Apr. 8, 1966, Ser. No. 541,188 3 Claims. (Cl. 229-25) The present invention relates to an egg carton and more particularly to an egg carton of thermoformed foamed plastic material.

There are various advantages in the use of a foamed plastic material in an egg carton; for example, the plastic material can be shaped to provide a more attractive package with pockets that will confine the eggs more close, the surface finish of the plastic material is relatively attractive in comparison to other materials and can be made white and clean-looking in color Without making the eggs look dirty since, because of its inherent reflectivity, the color of the interior of the package will appear to take the color of the eggs, the energy absorption characteristics of the walls are greater than with other materials so that there is a reduced tendency for breakage during loading or in shipment or handling of the carton, the material is relatively strong and light in weight, the material will effectively insulate the egg so that there are minimum temperature variations when the eggs are removed from and returned to refrigeration and therefore a reduced tendency for deterioration of the egg because of the temperature changes, and the carton is impervious so that if one egg is accidentally broken it will not contaminate other eggs in the same carton or in other cartons and the damage is thereby confined.

The objects of this invention are to provide an egg carton of a foamed plastic material, which carton is relatively inexpensive to manufacture, can be nested in a minimum of space to facilitat shipment and storage, can be readily de-nested, constitutes a minimum size package when filled, is relatively rigid and will not warp excessively, as for example, when the loaded carton is lifted by one corner, is sufliciently versatile to accommodate a number of different sizes of eggs, is so formed that the eggs may be readily removed when the carton is opened, and which at the same time affords a maximum of protection for the contents of the carton and constitutes an attractive package.

Briefly, the egg carton in accordance with this invention comprises a base member divided by partitions into a plurality of egg-receiving pockets and a pair of complemental cover members hinged to the upper edges of the side walls of the base member and adapted to be swung inwardly into a position overlying the base member. Means in the form of slotted posts are provided in the base member to receive the edges of the cover members and frictionally to hold the same in the close position and to support the same in spaced relation to the eggs in the carton, thereby permitting stacking of the filled cartons. Basically, the invention resides in the configuration and dimensioning of the base member and cover members to facilitate thermoforming of the carton from a sheet of foamed plastic material of minimum size, while at the same time permitting nesting of the cartons, providing a maximum of protection for the eggs when the cartons are filled, and which has a minimum overall dimension that is compatible with existing handling equipment.

With the above and other objects in view, a presently preferred embodiment of the invention is hereinafter described with reference to the accompanying drawings, in which:

' FIG. 1 is a perspective view of an egg carton con- 3,307,765 Patented Mar. 7, 1967 structed in accordance with this invention and with one of the cover members partially broken away and illustrated in phantom in the open position.

FIG. 2 is a fragmentary top plan view of the egg carton of FIG. 1.

FIG. 3 is a fragmentary transverse sectional view taken substantially on the line 33 of FIG. 2.

FIG. 4 is a fragmentary longitudinal sectional view taken substantially on the line 44 of FIG. 2 and illustrating the carton with the cover thereof in closed position.

FIG. 5 is a fragmentary transverse sectional view similar to FIG. 3 but on an enlarged scale and with the cover members closed.

With reference to the drawings, the present invention is illustrated as embodied in an egg carton thermoformed from a sheet of any suitable foamed plastic material, for example, polystyrene, polyethylene, polypropylene, copolymers of ethylene and propylene, and the like. Basically, the carton comprises a tray-like base member 1 and a pair of generally U-shaped cover members 2, each of which is hinged along one edge to an upper longitudinal edge of the base member 1 by an integrally formed hinge 3 and is adapted to overlie a portion of the base member 1. The hinge 3 may be of the type and may be formed in the manner that is disclosed and claimed in my copending United States patent application Serial No. 541,- 189, filed April 8, 1966.

The illustrated egg carton is of the standard 2 x 6 type in which there are one dozen egg-receiving pockets 4 arranged in two rows of six pockets each. The outer wall of the carton is formed by a pair of opposed side walls 5 and a pair of opposed end walls 6. At its top, the carton is open with the uppermost edge of the walls 5 and 6 defining a top plane 7. The bottom of the carton, which is discontinuous, consists of the individual substantially square bottom walls 8 of the pockets 4, all of which are formed in a bottom plane 9 and may be cushioned. Internally, the carton is divided longitudinally along its center line by a longitudinal partition 10 and transversely by five transverse partitions 11 parallel to and equally spaced longitudinally of the carton from each other and from the end walls 6. The partitions 10 and 11 are each substantially in the form of an inverted V, the longitudinal partition 10 having side walls 12 and a smoothly rounded top edge .13. and the transverse partitions 11 each having side walls .14 and a smoothly rounded top edge 15.

The side walls 5 each consist of substantially planar panels 16 interrupted at spaced intervals by the indentations 17, FIG. 3, there being one of the indentations 17 for each of the transverse partitions 11 with the apex 18 of each indentation being aligned with and merging smoothly into the top edge 15 of the respective partition 11. The indentations 17 have side walls 19 which extend downwardly toward the corners of the bottom walls 8 and which merge smoothly along their side edges with the panels 16 and with the side walls 14 of the transverse partitions 11. The side walls 19 thus constitute the outer corner walls of the egg-receiving pockets 4. The tops of the indentations 17 are closed by a triangular shaped panel 20 that is disposed slightly below the top plane 7 so that it will not interfere with closing the cover members 2. The panels 16 consist of a lower section 21 that constitutes the outer longitudinal wall of the eggreceiving pockets 4 and an upper section 22, both of which are substantially planar. The lower section 21 extends upwardly and outwardly from the outer edge of the bottom wall 8 at an angle of about sixty degrees to the bottom plane 9. The upper section 22 extends upwardly and outwardly from the top of the lower section 21 at an angle that is more nearly normal to the plane 9, or more particularly, at an angle of about seventyfive degrees to the plane 9.

The end walls 6 each consist of substantially planar panels 23 interrupted at the longitudinal center line of the carton by an indentation 24, FIG. 4, having an apex 25 that is aligned and merges smoothly with the top edge 13 of the longitudinal partition 10. The indentations 24 have side walls 26 that extend downwardly toward the corners of the bottom walls 8 and which merge smoothly along their side edges with the panels 23 and with the side walls 12 of the longitudinal partition which walls 26 constitute corner Walls of the egg-receiving pockets 4. The top of each of the indentations 24 is closed by a triangular shaped flange 27 that is disposed substantially in the top plane 7. Each of the panels 23 constitutes the outermost transverse wall of the end ones of the egg-receiving pockets 4 and consists of a lower section 28 and an upper section 29, both of which are substantially planar. The lower section 28 extends upwardly and outwardly from the edge of the bottom wall 8 at an angle of about sixty degrees to the bottom plane 9. The upper section 29 extends upwardly and outwardly from the top of the lower section 28 at an angle of about seventy-five degrees to the bottom plane 9.

At each of the corners of the carton, there is provided a corner wall 30 that is similar to the side walls 19 and 26, and which extends downwardly toward the corner of the bottom wall 8, and which have side edges that merge smoothly with the panels or side walls 16 and 23 of the pockets 4.

At the intersection of the longitudinal partition 10 with each of the transverse partitions 11, there is provided an upstanding post which is either a fiat-topped, cover-supporting post 31 or a slotted cover-retaining post 32. There are five of the posts 31 and 32 which are disposed in an alternating arrangement with three cover-retaining posts 32 disposed one each in the center and the two outermost positions, and with two of the cover-supporting posts 31 disposed one each in the tWo intermediate positions.

The cover-supporting posts 31 each consist of a flat top 33 that is disposed substantially in the upper plane 7 of the base member 1 and is arranged with the corners thereof disposed substantially over and merging smoothly with the top edges 13 and of the partitions 10 and 11, respectively. Depending from the edges of each of the tops 33 are side walls 34 that extend downwardly toward the corners of the respective bottom walls 8 and which merge smoothly along their side edges with the adjacent walls 12 and 14 of the partitions 10 and 11. The side walls 34, which are similar to the walls 26 and which constitute one of the inside corner walls of the pdckets 4, diverge downwardly at angles of about seventy-five degrees to the planes 7 and 9.

Each of the cover-retaining posts 32 consists of side walls 35 that are arranged in a pattern that defines a substantially square cross-section in planes parallel to the top plane 7. The edges of the posts 32 between the walls 35 are disposed substantially over and merge smoothly with the top edges 13 and 15 of the partitions 10- and 11, respectively. The side walls 35 extend downwardly toward the bottom wall 8 at angles of about seventy-five degrees to the bottom plane 9, and the side edges thereof merge smoothly with the adjacent walls 12 and 14 of the partitions 10 and 11. The walls 35 constitute the corner walls of the pockets 4 that are opposed to the walls 34 of the posts 31. The posts 32 extend above the top plane 7 and have a slot 36 extending inwardly from the free or upper end thereof. The slot 36 is arranged with the center thereof in a plane longitudinally of the base member 1 and normal to the top plane 7. The slot 36 is designed to receive edge portions of the cover members 2 and is less in width than the combined thickness of the edge portions of both cover members so that the edge portions will be frictionally held in the slot to insure that the to the transverse plane of maximum diameter.

covers will be held closed. The bottom of the slot 36 is located below the plane 7 to insure that the leading edges of the cover members 2 will not contact the bottom before the covers are fully closed. The top of each of the posts 32 is sloped inwardly from the outer corner thereof toward the slot to guide or cam the leading edge of the cover members 2 into the slot 36.

The cover members 2 are each generally U-shaped in transverse cross-section and include a top wall 37 and a depending skirt portion including an inclined side wall 38 at an angle of about sixty degrees to the top Wall 37 and along the edge 39 of which the hinge is formed, a normal side wall 40 opposite to the side wall 38 and at an angle of substantially ninety degrees to the top wall 37, and opposed end Walls 41 extending between the two side walls.

The cover members 2 are dimensioned such that when closed as illustrated in dotted lines in FIG. 3, that is, with edge portions at the leading or free edge 42 of the side walls 40 inserted in the slots 36 of the posts 32 and the free edges 42 seated on the tops 33 of the posts 31, the side walls 40 of both cover members are substantially normal to the top plane 7 of the carton with the outer surfaces of the walls 40 in contact or in abutting relation to each other, and the top wall 37 is substantially in spaced parallel relation to the top plane 7, thereby atfording a flat substantially unbroken surface for receiving indicia.

Formed in the normal side wall 40 of each of the cover members 2 is a pair of notches 43, each of which is substantially semi-conical, with the base thereof at the top wall 37 of the cover member and the apex thereof adjacent to the free edge 42 of the wall 40. The notches 43 are designed to receive the thumbs of the user to facilitate opening the cover member 2, which would otherwise be quite difiicult in view of the fact that the side walls 40 of the cover members 2 are in abutting relation and afford no opening or hand hold by means of which the user could grasp the cover members 2 to open them. In the illustrated embodiment, the notches 43 in each of the cover members are opposed so that the total thumb hole afforded by the combined notches 43 is substantially conical.

The notches 43, which are disclosed and claimed in my co-pending 'United States patent application Serial No. 541,200, filed April 8, 1966, also function to add stiffness to the carton and to prevent twisting or warping thereof, as for example, when the loaded carton is lifted by one corner. For this reason, the notches 43 are located longitudinally of the wall 40 on opposite sides of and substantially in engagement with that portion of one or more of the posts 32 that extends above the plane 7, whereby the engagement of the notches 43 with the post or posts 32 will prevent sliding of the walls 40 in both directions in the slots 36.

The depth of base member 1, that is, the distance between the top plane 7 and the bottom plane 9, is selected at the average dimension from the point of the egg for which the carton is designed to the level of the plane of maximum diameter thereof, the point of the egg being the so-called small end thereof. While the specific shape of eggs varies significantly, there is a relationship that exists between the length and the maximum diameter of an egg of a given weight range and the location of the plane of maximum diameter lengthwise of the egg. For example, based upon the measurement of twelve dozen chicken eggs, graded Extra Large, that is, eggs having a weight of between 2.25 and 2.50 ounces, the average overall length was 2.380 inches and the average distance from the point or small end of the eggsto the transverse plane of maximum diameter was 1.250 inches. The range over which the actual measurements of all of the eggs varied from these average measurements was 0.447 inch for overall length and 0.375 inch for the distance from the point Thus,

the average ratio of the distance between the transverse plane of maximum diameter and the point of the egg to the distance from this plane to the opposite or large end of the egg is slightly less than 2 to 1. For all of the eggs measured, this ratio varied between a maximum of 2.19 and a minimum of 1.74. Stated differently, the distance from the plane of maximum diameter to the point of the eggs constituted about 66% of the overall length of the eggs on the average, and varied between about 63% and 69%. Accordingly, the transverse plane of maximum diameter of an egg is oif-center lengthwise of the egg so that the longitudinal dimension of the egg in the opposite directions lengthwise of the egg from the plane are unequal. At thesame time, since the depth of the base member 1 and of the cover members 2 are, in accordance with this invention, dimensioned relative to the dimension lengthwise of the egg in opposite directions from the plane, they are necessarily unequal. The above construction produces significant advantages over the construction heretofore employed in the prior art devices wherein the depth of the base member was made substantially equal to one-half the length of the egg and the depth of the base member was therefore substantially equal to the depth of the cover member. With the top plane 7 disposed substantially at the level of the transverse plane of maximum diameter of the egg as herein contemplated, not only are the edges 42 of the cover member dispose-d in an optimum relation to the egg for confining the same, as seen in FIG. 5, wherein an egg E is illustrated in phantom, but also the depth of the side wall 5 is increase-d, thereby providing greater strength and stiffness longitudinally of the base member 1. At the same time, the depth of the section along the longitudinal center line of the base member 1 is significantly increased, that is, the distance in the longitudinal center plane normal to the top plane 7 from the bottom of the slot 36 to the bottom of the top edge 13 of the longitudinal partition 10. Generally, the depth of this section is limited since, although it is desirable to make the top edge 13 as low as possible to provide sufiicient strength and to facilitate removal of the eggs, the wall must also be sufficiently high to maintain separation of the eggs. This increased section substantially strengthens and stilfens the base member laterally, thereby reducing the tendency for the base member to bend about its longitudinal center line when, for example, the loaded carton is lifted by one side, which bending tends to open or expand the slot 36 and thus permit the cover members 2 to open.

The alternating arrangement of the cover-retaining posts 32 and the cover-supporting posts 31 are disclosed and claimed in my co-pending United States patent application Serial No. 541,187, filed April 8, 1966. The advantages of this arrangement is that it not only provides means for frictionally holding the cover members 2 closed, but, with the wall 40 of the cover member 2 on edge on the posts 31 and on the flange 27, it also provides support for the top 37 of the carton so that the filled cartons can be stacked one on top of the other in a shipping case. A further advantage of this arrangement is that, during forming, the sheet which has been heated to forming temperature initially engages the tops of the mold sections for forming the posts 32 and tends to sag or drape between the same along a line that in the finished carton becomes the top edge 13 of the longitudinal partition 10. As the sheet sags or drapes, the portion midway between the posts 32 doubles onto itself or pinches together below the line 13 defined by the top edge to produce a thickened section at this point as shown at 44 in FIG. 5. This thickened section further strengthens the base member 1 against flexing laterally or about its longitudinal center line and also provides an addition-a1 thickness of material for use in forming the positioning surfaces that determine the stack or nesting height as is hereinafter more fully explained.

In order to facilitate storage, handling and transportation of the cartons before they are filled, they must be made so that they can be stacked or nested in a minimum of space and they must be sufliciently uniform in stack height, which is herein used to designate the distance from the flange 27 of one carton to the flange 27 of the adjacent cartons in the stack, so that they can be readily de-nested mechanically.

In nesting the cartons, the stack height is a function of the angles and the thicknesses of the walls, that is, as the angles of the walls are made progressively more normal to the planes 7 and 9, the thickness of the wall that can be accommodated within a given stack height is progressively reduced. Generally, the objective is to provide nesting of. the cartons within one-quarter of an inch, which is the standard dimension that provides a sufficiently compact stack and which is also the dimension upon which commercial de-nesting machines are designed to operate. While it is desirable from the standpoint of costs to form the carton from a sheet of minimum thickness, it is also necessary that the sheet from which the carton is formed is sufliciently thick to permit forming and that the finished and filled carton will have sufiicient strength and rigidity for normal handling, as well as provide cushioning for the contents. For this reason, the minimum foam thickness that can be used successfully is about one-sixteenth of an inch. With a foam of this thickness, walls that are at an angle of fifteen degrees to the plane normal to the planes 7 and 9 can be accommodated within the one-quarter inch stack height. This angular dimension is also significant from the standpoint that it is also possible to work the plastic sheet in thermoforming on a commercial basis to provide walls that are thus seventy-five degrees out of the original plane of the sheet.

To provide the necessary accuracy in the stack height so that the cartons can be successfully de-nested with commercial machines, the thickened sections 44 of the partitions 10 are accurately formed both top and bottom to the desired dimension, e.g., one-quarter inch, and are uniformly disposed with respect to the flange 27, which is the surface acted upon by the de-nesting equipment. Thus, when the cartons are stacked, it is always the thickened sections 44 that are in engagement and determine the stack height. While each carton may tilt laterally about its longitudinal center line to a certain extent, the flanges 27 are also disposed at the center line and thus the stack height is not disturbed.

The cover members 2 are formed integrally with the base member 1. In order to provide for nesting of the cartons and also to facilitate forming, the side walls 38 of the cover members as hereinbefore noted are at an angle of about sixty degrees to the top wall 37. During forming and during nesting, the cover members 2 are disposed at one hundred and ninety-five degrees about their hinges 3 from their closed positions. In this position, the side walls 38 and 40 of the cover members 2 are both disposed at angles of seventy-five degrees to the top plane 7 of the base member. The inclination of the side wall 38 is also compatible with the overall dimension of the carton, as hereinafter noted, while acting closely to confine the eggs in the pockets 4.

A further consideration that must be accommodated in the design of the carton is the overall dimension. In view of the large volume of existing equipment for handling egg cartons, and also to minimize expenses in storage and shipment, the cartons must be of a size that is comparable to the relatively small size of present egg cartons. By extending the side walls 38 of the cover members 2 at the designated angles and terminating them in the plane 7, which is substantially at the plane of maximum diameter of the egg, the walls 38 not only closely clear the egg for confining the same, but also extend laterally from the longitudinal center line of the carton a distance that is substantially equal to the comparable dimension of existing cartons. At the same time, the panels 22 of the side walls 16 are disposed at the desired angle for purposes of stacking and forming.

In the egg carton formed in accordance with this invention, each of the egg-receiving pockets 4 comprises a substantially square bottom wall 8, substantially planar side walls, i.e., the walls 12, 16, 14 and 28, that diverge upwardly from the edges of the bottom wall 8 at angles of about sixty degrees to the top and bottom planes 7 and 9 of the base member 1, and corner walls, i.e., the walls 34 or 35 or 26 along the longitudinal partition 10 and the walls 19 or 30 along the side walls 5, which corner walls are either planar or slightly convex and which extend between the adjacent ones of the side walls and are disposed at angles of about seventy-five degrees to the planes 7 and 9. While the lower portion of an egg seated on the bottom wall 8 is closely confined by the side walls and the corner walls of the pockets, the upper portion of the egg is also closely confined by the top wall 37 of the cover member 2, as well as by the side wall 40, which may engage the egg at its transverse plane of maximum diameter, and by the inclined side wall 38. Formed in this manner, and with dimensions selected to accommodate the maximum dimensions of the egg for which the carton is designed, there is provided a carton in which the eggs are snugly confined to prevent them from moving about within the carton, and which, because of the inherent resiliency of the foamed material, are well cushioned to protect them against breakage. At the same time, the carton is so dimensioned that it can be thermoformed and can be nested and de-nested, has sutficient strength and rigidity for normal handling and stacking when filled, has overall dimensions that are compatible wtih present handling equipment, and also has the covers thereof securely held in the closed position and yet can be readily opened by the average user.

What I claim and desire to protect by Letters Patent is:

1. An egg carton formed of foamed plastic comprising a tray-like base member having a top plane and a bottom plane that is parallel to the top plane and spaced therefrom a distance substantially equal to the dimension from the point to the transverse plane of maximum diameter of the largest egg adapted to be received in the carton, said base member having side walls and end walls extending between the planes, longitudinal and transverse partitions dividing the base member into rows of egg-receiving pockets, and a bottom wall for each of said pockets disposed in the bottom plane, said partitions having side walls which together with the side walls and end walls of said base member are disposed at angles of not greater than approximately seventy-five degrees to the bottom plane, and a U-shaped cover member having a hinge connecting the same to the side wall of the base member along a line in the top plane for swinging between the closed position overlying the base member and an open position that is substantially one hundred and ninety-five degrees from the closed position, said cover member having a top wall that in the closed position is disposed in parallel relation to the top plane and spaced therefrom a distance that is substantially equal to the dimension from the end opposite the point to the transverse plane of maximum diameter of the largest egg adapted to be received in the carton, a normal side wall normal to said top wall and having a free edge that is disposed substantially in the top plane when the cover member is closed, and an inclined side wall along the edge of which the hinge is formed and which is disposed at an angle of substantially sixty degrees to the top plane, whereby said normal side wall and said inclined side wall of said cover member are both disposed substantially at angles of seventy-five degrees to the top plane when said cover member is in the open position.

2. An egg carton in accordance with claim 1 in which the side walls of said partitions are disposed at angles of substantially sixty degrees to the bottom plane and the side walls and end walls of said base member include planar lower portions disposed at substantially sixty degrees to the bottom plane and planar upper portions that are disposed at substantially seventy-five degrees to the bottom plane.

3. An egg carton in accordance with claim 1 in which there is provided one longitudinal partition disposed substantially at the longitudinal center line of the base member and a pair of cover members hinged along the opposite side walls of the base member and having the normal side walls thereof disposed in abutting relation and substantially overlying the longitudinal partition when said cover members are in the closed position.

References Cited by the Examiner UNITED STATES PATENTS 2,466,579 4/ 1949 Cox 229-2.5 2,634,039 4/ 1953 Schwerfeger 229-25 X 2,778,558 1/1957 Butterfield 229-29 2,933,227 4/ 1960 Vahle 229-25 3,093,286 6/1963 Brickner et a1. 229-25 3,184,133 5/1965 Boyd et al. 229-29 X 3,191,844 6/ 1965 Comstock 229-2.5

GEORGE O. RALSTON, Primary Examiner. 

1. AN EGG CARTON FORMED OF FOAMED PLASTIC COMPRISING A TRAY-LIKE BASE MEMBER HAVING A TOP PLANE AND A BOTTOM PLANE THAT IS PARALLEL TO THE TOP PLANE AND SPACED THEREFROM A DISTANCE SUBSTANTIALLY EQUAL TO THE DIMENSION FROM THE POINT TO THE TRANSVERSE PLANE OF MAXIMUM DIAMETER OF THE LARGEST EGG ADAPTED TO BE RECEIVED IN THE CARTON, SAID BASE MEMBER HAVING SIDE WALLS AND END WALLS EXTENDING BETWEEN THE PLANES, LONGITUDINAL AND TRANSVERSE PARTITIONS DIVIDING THE BASE MEMBER INTO ROWS OF EGG-RECEIVING POCKETS, AND A BOTTOM WALL FOR EACH OF SAID POCKETS DISPOSED IN THE BOTTOM PLANE, SAID PARTITIONS HAVING SIDE WALLS WHICH TOGETHER WITH THE SIDE WALLS AND END WALLS OF SAID BASE MEMBER ARE DISPOSED AT ANGLES OF NOT GREATER THAN APPROXIMATELY SEVENTY-FIVE DEGREES TO THE BOTTOM PLANE, AND A U-SHAPED COVER MEMBER HAVING A HINGE CONNECTING THE SAME TO THE SIDE WALL OF THE BASE MEMBER ALONG A LINE IN THE TOP PLANE FOR SWINGING BETWEEN THE CLOSED POSITION OVERLYING THE BASE MEMBER AND AN OPEN POSITION THAT IS SUBSTANTIALLY ONE HUNDRED AND NINETY-FIVE DEGREES FROM THE CLOSED POSITION, SAID COVER MEMBER HAVING A 